This invention relates generally to load stabilizing mechanisms for use in the logging industry and particularly to a chain for the prevention of slippage of logs on a transport platform.
As is well known to those skilled in the logging industry, trees are harvested and transported to processing facilities for use in a number of diverse industries, among which industries are the pulp wood industry and the lumber industry. Logs for use in the pulp wood industry are generally cut into lengths of from 5 to 8 feet at the logging site, and the logs so cut are piled in sections on a logging truck with their lengths transverse to the bed of the truck. In practice, a so-called bob-tail truck will accept two such piles or sections, while longer trucks such as tandems or tractor-trailers may accept as many as five sections.
Logs for use in the lumber industry are cut in much longer lengths, consistent with their desired end use, and are piled in a single section on a logging truck with their lengths parallel to the length of the bed of the truck.
In the case of pulp wood logs, the bed of the truck is equipped with upstanding barriers, placed transversely to the truck bed, which serve to separate each section of logs, and to prevent the intermingling of logs from adjacent sections. Such barriers conventionally comprise two upstanding members secured to opposite sides of the truck bed and a cross-member connecting the tops of the upstanding members. The size of each section of logs is predetermined to hold that number of logs which may be easily accommodated by mechanical gripping and lifting devices utilized to remove the logs from the truck at the pulp mill site. In the case of lumber logs, the bed of the truck is equipped with a number of freely upstanding posts mounted to and located along each side of the bed of the truck, which posts serve to prevent the logs from rolling off the sides of the truck.
In each of the two types of transportation operations described above, it is well known to utilize either "chain and binder" or "cable and winch" systems to further protect against the possibility of logs falling from the bed of the truck during transportation. For pulp wood logs, one end of a chain is generally secured to the cab of the truck, or to the upstanding barrier immediately rearwardly adjacent the cab, by suitable interconnecting means, at a point intermediate the width of the load, and the remainder of the chain placed over the sections along the length of the truck bed. The second end of the chain is then immobilized at the rear of the truck bed and the chain tightened by a suitable over-center binder. For lumber logs, a chain is wrapped about the entire pile of logs at a point intermediate their length and the chain secured and tightened by a suitable over-center binder. As will be readily understood, in each operation, the chain is placed transverse to the length of the logs and the chain is tightened by the binder so as to maintain as tight a hold on the logs as possible.
For the purpose of simplicity in the following description slippage of logs in a direction parallel to their length will be termed longitudinal slippage and slippage in a direction perpendicular to their length will be termed lateral slippage.
Illustrative of "chain and binder" securing mechanisms are those disclosed in U.S. Pat. Nos. 448,862 to Johnson and in 3,271,007 to Ratcliff. Each of these patents discloses an apparatus for binding the logs to the truck bed in which an over-center load binder is used to tighten a chain about a load of logs in order to prevent slippage. Each patent discloses the use of a conventional chain comprising individual links in combination with an over-center load binder. A third example of a load binding apparatus embodying an over-center load binder is disclosed in U.S. Pat. No. 2,919,895 to Johnson which shows the binder mounted to the bed of the truck at the rear end thereof, in order that an operator may be safely out of the path of logs which may be displaced during operation of the binder.
While each apparatus for stabilizing logs described hereinabove, and similar systems in conventional use, the proven generally satisfactory, each suffers from at least two major disadvantages. The first such disadvantage stems from the fact that, since the chain or cable used to bind the logs depends only on the tightness or tension exerted on the pile of logs to hold the logs securely, constant jarring over long haul distances may cause the logs to pack more tightly together and may thereby tend to slacken the tension of the chain and loosen the load. The second such disadvantage is that, although lateral slippage is relatively well prevented by a conventional chain and binder apparatus due to its orientation transverse to the length of the logs, such systems offer a great deal less protection against longitudinal slippage of the logs, especially when the load is subjected to sudden forces such as frequently occur in a traffic accident. Indeed, the problem of slippage is of such magnitude that the State of Alabama has passed legislation requiring that pulp wood trucks have their load secured by a minimum of two chains or cables rather than one.
There is thus a need for a log stabilizing apparatus which will more securely hold logs with respect to both lateral and longitudinal slippage despite minor decreases in chain or cable tension which occur during transportation.